Fourth generation mobile telecommunication systems, such as those based on the 3GPP defined UNITS and Long Term Evolution (LTE) architecture are able to support more sophisticated services than simple voice and messaging services offered by previous generations of mobile telecommunication systems.
For example, with the improved radio interface and enhanced data rates provided by LTE systems, a user is able to enjoy high data rate applications such as mobile video streaming and mobile video conferencing that would previously only have been available via a fixed line data connection. The demand to deploy fourth generation networks is therefore strong and the coverage area of these networks, i.e. geographic locations where access to the networks is possible, is expected to increase rapidly.
The anticipated widespread deployment of fourth generation networks has led to the parallel development of a class of devices and applications which, rather than taking advantage of the high data rates available, instead take advantage of the robust radio interface and increasing ubiquity of the coverage area. Examples include so-called machine type communication (MTC) applications, which are typified by semi-autonomous or autonomous wireless communication devices (i.e. MTC devices) transmitting and receiving small amounts of data on a relatively infrequent basis. Examples include so-called smart meters which, for example, are located in a customer's house and periodically transmit information back to a central MTC server data relating to the customers consumption of a utility such as gas, water, electricity and so on.
The nature of MTC devices may lead to their disposal in locations where communication with mobile telecommunications systems such as those mentioned above may prove unreliable, even when taking into account increasing coverage. For instance, MTC devices such as smart meters may be located in the basement of a house or other hard to reach locations where signals from mobile telecommunications system may not be received at a sufficient strength because they have propagated over highly attenuating channels. Consequently, devices such as smart meters may be unable to perform reliable detection and estimation of data conveyed by the signals. Scenarios such as this may also occur when devices are near the border of a geographic area served a by mobile telecommunications system. Overcoming these problems by further extending the coverage of mobile communications networks would allow an increased number of devices to be supported by mobile communications networks.
The use of decreased coding rates and reduced order modulations schemes present a potential solution to improving the reliability of detection and estimation of data at a device. However, often a restricted set of possible modulation and coding rates are supported by devices, especially low cost ones such as MTC devices, and therefore improvement via coding changes may be limited. Recently it has been suggested that transmission repetition may present an alternative solution to extending coverage to mobile devices which are currently unable to be reliably served by a mobile communications network.